Well, a proton is UUD and a neutron is UDD - so the interaction would have a UU and a DD pair. the UD combo I dunno about. I suspect that it would absorb a bit of the energy of the pair annihilation and end up as a UD and a DU meson/antimeson pair, which might or might not have sufficient kinetic energy to leave the scene of the crime.

It would -not- be as strongly preferred an interaction as a particle/antiparticle pair.

nick012000 wrote:Out of curiosity, what happens when an anti-proton hits a neutron, or vice-versa? Near as I can tell, you'd wind up with either wandering quarks (which I've read is impossible, due to the force gluons create increasing with distance), or some bizarre new particle composed of both matter and antimatter. Any of you physics folks willing to chime in here?

Believe it or not, the experiment was already undertaken in Italy. According to this abstract, the end result was a threebody final state: Kaon/Anti-Kaon/Pion. (From the later Columbia research.)

Kerry Skydancer wrote:Not quite. That's an antiproton-deuteron interaction. Both the neutron and the proton of the deuterium nucleus are playing, which is why you still have a net plus-one baryon number at the end.

The kaon-antikaon pair is an interesting result, though, especially since kaons are as close to mixed matter-antimatter as you're going to find. Very strange little particles.

Antiproton-proton anihilation yields two photons in the X-ray range. Therefore, any other result is likely to be from the neutron's annihilation.

Two or three photons, depending on whether the proton-antiproton pair have opposing or synchronous spin, actually. All kinds of weird conservation laws in there. But yes. Something other than pure energy coming out indicates that the neutron got involved.